xc2xa71.1 Field of the Invention
The present invention concerns air handling and HVAC systems. More specifically, the present invention concerns eliminating snow from air entering an air handling or HVAC system.
xc2xa71.2 Related Art
The present invention may be used with factory built air handling systems or field built HVAC systems, or may be retrofitted (e.g., in the field) into existing HVAC systems. Air handling systems channel outside air into the ventilation system of buildings. Air handling systems are described further in xc2xa71.2.1. Then, the need for extracting snow from air entering air handling systems is introduced in xc2xa71.2.2. Finally, three known techniques for extracting snow from an air stream, as well as their perceived shortcomings, are described in xc2xa71.2.3.
xc2xa71.2.1 Air Handling Systems
Air handling systems supply fresh outside air to buildings. Air handling systems are often located on the roof of the building. The air is transferred throughout the building via a ventilation system, and may be processed along the way (e.g., heated, cooled, humidified, dehumidified, filtered, etc.). An air handling system typically includes a supply fan, pre-filters, filters and air processing units (e.g., heating coils, cooling coils, steam humidifiers and intake dampers). The components of the air handling system are typically enclosed in one or more rectangular structures. These structures are typically fabricated from steel and/or aluminum.
The supply fan controls the flow of the air entering the air handling system, and particles and contaminants are filtered out of the air by the pre-filter and the filter. The incoming air may also be processed, for example, the air may be heated on a cold day, or cooled on warm day, before it is injected into the ventilation system of a building.
xc2xa71.2.2 The Need for Extracting Snow
Problems occur in climates where snow is mixed with the air stream entering an air handling or HVAC system. Air filters can clog with frozen snow slush or ice, under snowy conditions, and their ability to filter out particles and contaminants may be compromised. In addition, the clogged filters can disrupt normal airflow and can stress the supply fan(s). Indeed, snow blocked filters can block air flow to vital areas or rooms of a buildings interior. This can create sever hazards in some instances. Therefore there is a need to extract snow from the air stream entering an air handling or HVAC system. Such snow extraction should occur before the snow would otherwise contact air filters. xc2xa71.2.3 Known Techniques for Extracting Snow and their Perceived Shortcomings
There are known techniques for extracting snow from air streams. Such techniques include deploying air unit heaters, preheating coils, or mesh pads or grids. Forced air unit heaters are discussed in xc2xa71.2.3.1, auxiliary pre-heating coils in xc2xa71.2.3.2, and metallic mesh pads or woven mesh grids in xc2xa71.2.3.3. Unfortunately, however, each of these known techniques is believed to have limitations and disadvantages. xc2xa71.2.3.1 Forced Air Unit Heater
A forced air unit heater technique for extracting snow from air streams uses a heated water and/or glycol solution and/or low-pressure steam to heat a first (ingress) section of an air handling system. The first section of an air handling system may be the section immediately following the air intake dampers. As air mixed with snow enters the air handling system, it passes through the heated section and the snow is semi-effectively removed from the air. The drawbacks to this method include a high initial cost, high operating costs, and high maintenance costs.
xc2xa71.2.3.2 Auxiliary Pre-Heating Coils
Another technique for extracting snow from air streams includes providing auxiliary pre-heating coils that include numerous rows of hollow tubes with heat radiating fins attached to the tubes. Hot water and/or glycol is passed through the tubes and heats the fins. When snow mixed air passes through the pre-heating coils, the snow comes in contact with the fins and melts. The drawbacks of this method include a high initial cost, high operating costs, and high maintenance costs. In the summer the auxiliary pre-heating coils need to be protected by a pre-filter, or the pre-heating coils should be removed. This added requirement increases the maintenance costs.
xc2xa71.2.3.3 Metallic Pads or Woven Mesh Grids
A third technique for extracting snow from air streams includes metallic pads or woven mesh grids with electric radiant heaters and/or a series of electric elements to melt snow. The apparatus described by Kane in U.S. Pat. No. 5,791,984 uses this third technique. The drawbacks of this method include a high initial cost, high operating costs, and high maintenance costs. In addition, the mesh pad element used to capture snow also acts as a filter trapping particles, contaminates and water. This may potentially lead to health risks, for example, mold and/or fungus growing on a mesh pad and being injected into the ventilation system of a building. The filtering effect may also lead to clogging of the mesh pad with snow, ice, or slush, disrupting normal airflow and stressing the supply fan. This technique may also require swapping the apparatus with a pre-filter as the seasons change, increasing maintenance costs.
Another drawback of metallic pads or woven mesh grids is that some of them employ xe2x80x9cmodularxe2x80x9d type panels. Each panel has an electrical connection to the next panel. These electrical connections offer points where corrosion may occur, and points where the electrical contact of the melting elements may break. Continued checkups on these connections are necessary and therefore increase maintenance costs.
xc2xa71.2.4 Unmet Needs
Accordingly, there is a need for a snow extracting technique that has a low initial cost and low operating and maintenance costs, and that minimizes or eliminates potential health risks associated with mold or bacteria growth in the snow extracting element. The snow extractor should be positioned before any air filters in an air handling system to prevent the air filter from becoming clogged. In addition, the heating element should minimize or avoid connection points where corrosion or breaks may occur. The snow extractor should be able to be used in factory built air handler systems, or field built HVAC systems. Further, the snow extractor should be able to be retrofitted into existing air handler and HVAC systems.
The present invention provides an apparatus for extracting snow from the air entering an air handling or HVAC system. This apparatus basically includes a plate and means for heating the plate. The plate is bent along a plurality of vertical axes to define a series of connected xe2x80x9cVIxe2x80x9ds having an alternating series of edge points and pockets and has perforated holes. The pockets may be flattened to form a trough, though they needn""t be.
The means for heating the plate may be a heater core including vertical runs provided adjacent to the (flattened) pockets on a second side of the plate. A control element for sensing snow mixed with air entering an air handling system may also be provided. Such a control element may be adapted to activate the heater core when snow is detected, and to deactivate said heater core when snow is no longer detected
The apparatus may further include heater core retainers being placed over the vertical runs of the heating coil to hold the heater core to the plate, and/or deflectors being bent along a vertical axis located in the middle of the deflector. The deflectors may be situated on the points of the first side of the plate. The deflectors may deflect entering air towards a hottest part of the plate.
The plate and the means for heating the plate may be provided to produce a counter flow reaction in which extremes of warm and cold head towards each other.